The consistent combustion of fossil fuels such as petroleum, coal, etc. by humans has increased the production of greenhouse gases such as carbon dioxide and led to global warming. As a result, environmental destruction has proceeded globally and it has reached the stage where the fall of mankind has to be concerned about. To prevent such disaster for the earth and the human race, efforts to reduce the production of greenhouse gases such as carbon dioxide by decreasing the use of fossil fuels are necessary. In this regard, researches on the utilization of nuclear energy, solar energy and natural gas such as shale gas, whose main constituent is methane, are increasing recently.
However, as for the nuclear energy, the sources will be depleted some day and accidents may lead to catastrophic disaster. The solar energy is low in utilization efficiency and thus requires a very high cost.
Meanwhile, although the natural gas consisting primarily of methane releases carbon dioxide during combustion, the amount is ½ or less as compared to the fossil fuels such as coal, petroleum, etc. Accordingly, the global warming problem can be solved or greatly relieved. In particular, hydrogen produced underground from water splitting by natural rock, whose main components are solid acids, reacts with carbon compounds existing in underground rock formations, thereby producing natural gas such as shale gas. Only with the shale gas reserves proven thus far, it is estimated that the human energy needs can be satisfied consistently for at least 100 years. Accordingly, if it is possible to produce a synthesis gas based on the principle by which natural gas is produced, the energy problem of humankind may be solved ultimately without environmental destruction.
The processes wherein hydrogen is produced from water and methane gas is produced by reaction of the hydrogen with a carbon compound include an artificial process wherein coal is reacted with water at high temperature to obtain a synthesis gas and a natural process wherein natural gas such as shale gas is produced underground.
In the existing artificial process for producing a synthesis gas, a lot of air pollutants such as carbon dioxide are generated during the reaction of coal with water. In contrast, when hydrogen is produced naturally from water splitting by rock catalysts as in production of natural gas underground, oxygen generated as byproduct of the water splitting is removed as it is used to oxidize reductive materials existing in rocks.
The inventors of the present disclosure have recognized that, when water is split using a natural rock catalyst by mimicking the natural process described above and oxygen is removed by a reductive material existing in rock or when water is split using a solid acid catalyst and oxygen is removed by a reductive material such as iron and the produced hydrogen is reacted with a carbon compound to produce a synthesis gas having a compositional distribution similar to that of natural gas, production of environmentally destructive byproducts can be prevented or remarkably reduced.